1. Field of the Invention
The present invention relates to vibration monitoring sensors and equipment. More specifically, the present invention relates to the remote monitoring of the condition of rotating machinery with vibration sensors when it is difficult or unsafe to retrieve data from the sensors locally.
2. Description of the Related Technology
The need to accurately predict excessive wear, functional abnormalities, or the imminent malfunction of machines such as pumps, turbines, and the like is well known. It has become common to use vibration transducers which convert an operating machine""s mechanical vibrations into an electrical signal which can be analyzed for characteristics which indicate abnormal operation or the need for maintenance. It can be appreciated that resources can be more efficiently utilized in manufacturing facilities and other environments when machine failure can be predicted, and the machine fixed or replaced prior to catastrophic failure. Human safety is also improved if the incidence of significant machine malfunction is reduced or eliminated.
Two approaches have been used to generate the vibration data necessary to perform these monitoring functions. In some installations, a portable probe is carried around the facility by facility personnel, and is used to collect vibration data from various locations on the machinery being monitored. These portable probes may include an integral vibration transducer, or may utilize fixed transducers at the points to be measured. Such a system is described in U.S. Pat. No. 4,885,707 to Nichol, et al. In the apparatus disclosed by Nichol, a computer interface module is also included for communication of measurement parameters and vibration data between the portable probe and a host computer system at the facility.
An alternative design, one example of which is provided in U.S. Pat. No. 5,430,663 to Judd, et al., includes a plurality of fixed transducers connected by a common bus which interfaces with an on-site host computer system.
A variation of these two systems is disclosed in U.S. Pat. No. 4,621,263 to Takenaka, et al. In this system, a robot with a non-contact vibration sensor moves throughout the facility, communicating vibration data to a host computer system either with a hard-wired cable connection, or alternatively with a wireless communication link. This robotic device is stated to be especially useful in nuclear power plants, where the use of plant personnel to gather vibration data may expose people to unacceptable hazardous environments.
In all of the above-described systems, however, a locally based vibration monitoring presence is required. In most cases, monitoring personnel collect data at the machines themselves. In some cases, data is routed via communication cable to an on-site host monitoring computer which is itself manned by facility personnel. In many applications, however, it is infeasible to maintain any local presence for the purpose of vibration monitoring. Some pipeline sections, pumping stations, and the like may include a very small number of machines to be monitored, and be located tens or even hundreds of miles away from a suitable host location. In such situations, equipment is often allowed to run to failure because vibration monitoring to diagnose abnormalities cannot be performed.
There is accordingly a need in the art to provide remote vibration monitoring in a cost effective manner to allow efficient maintenance of such remote machines. To date, no long distance communication method has been considered and applied to this problem. It may be noted that satellite communication techniques have been applied to vibration data gathering in the electric power distribution industry, as is described in U.S. Pat. No. 5,029,101 to Fernandes, and in the railroad transportation industry, as is described in U.S. Pat. No. 5,433,111 to Hershey, et al. In these fields, however, installation and management of dedicated long distance communication links is often already performed for other purposes, and is also more economically justifiable for a huge number of railroad cars, for example, than when a fairly small number of stationary and remote machine installations must be monitored.
Furthermore, those of skill in vibration data collection and analysis at facilities having stationary rotating machinery are typically not trained or extensively exposed to digital electronics or communications technologies. This general unfamiliarity in the relevant art with the capabilities of these technologies has slowed their application to machine monitoring. In fact, the employment of digital technology in vibration data collection is often resisted as its use is perceived to introduce undesired complexities into facility management. A remote monitoring system should therefore be easy to install and use, and should require a minimum of specialized on-site electronics which must be configured and maintained by process control management.
The present invention provides an efficient and easily managed communication link between a remote stationary machine and a control room having a host control computer system for analysis of machine condition and process control. Most preferably, embodiments of the present invention allow wireless communication between the remote site and the host control facility over communication links supported by an existing infrastructure. This minimizes the amount of communications equipment which must be managed by facility managers, thereby freeing them to concentrate on bearing fault analysis and machine maintenance. In particularly preferred embodiments, a portion of the communication link between the monitored machine and the host control room comprises a paging network.
Thus, in one embodiment, the invention comprises a vibration monitoring system comprising a vibration transducer connected to vibrating machinery, signal conditioning circuitry configured to produce digital data indicative of the condition of the vibrating machinery, as well as a memory storing at least a portion of the digital data. The system may further comprise a page transmitter connected to the memory so as to transmit the digital data to a host computing system for analysis.
The invention also comprises methods of machine monitoring and methods of making vibration monitors. In one embodiment, a method of monitoring the condition of a machine comprises sensing a vibration level of the machine, storing the vibration level in a memory, and sending a page containing data from the memory to a host. In another embodiment, the invention comprises a method of making a machinery condition monitor comprising connecting a two-way page transceiver to a vibration transducer and connecting a memory to both the vibration transducer and the two-way page transceiver such that vibration data may be stored in the memory and forwarded to a host monitoring system via alphanumeric page messages.
These apparatuses and methods thus defined provide high quality vibration data communication links without requiring process control management to develop, install, and maintain an extensive collection of communication equipment.